Imbalances in microbial populations and growth of harmful bacteria in the digestive tract of animals can cause significant losses in animal growth and production. These imbalances manifest themselves as intestinal disorders such as diarrhea. While microbial infections of animals have been prevented by the use of e.g. antibiotics and other agents that prevent the growth of microorganisms, stricter regulations on their use are expected. Ruminant animals can utilize fiber-rich raw materials which have little or no nutritional value for monogastrics like the human. However, the feed conversion efficiency of ruminants is relatively low and their methane production represents a remarkable share of the world's greenhouse gas emissions. With the increasing demand of food there is a need to improve the feed conversion efficiency of ruminants and to lower their methane production. Generally, there is an increasing demand for ingredients for use in animal feeding that can modulate the microbial population in the animal digestive tract but which are readily available, well tolerated and environmentally friendly.
Fractional distillation of crude tall oil, obtained as a by-product of the Kraft process of wood pulp manufacture, produces distilled tall oil (DTO) which typically comprises over 10% resin acids and less than 90% fatty acids. Further refinement of distilled tall oil produces tall oil fatty acid (TOFA), which is available in a variety of compositions differing in the fatty acids and resin acids content. Because TOFA is an inexpensive source of fatty acids, it has previously been used in animal nutrition as an energy source. For instance, GB 955316 discloses the use of alkali metal salts of tall oil fatty acids to improve weight gain and nitrogen retention in ruminant animals.